1STM vs. LTM: 1 System or 2?Older View2 Systems w/Distinct CharacteristicsNewer ViewDifferent States in a Single SystemSTM vs. LTM: 1 System or 2? Capacity Duration Forgetting Coding RetrievalWorking Memory (Baddely) Central ExecutiveModality FreeResembles AttentionPhonological Loop (aka ArticulatoryLoop)Holds Speech-Based InfoVisuospatioal SketchpadSpatial and Visual CodingCentral Executive Limited Capacity Various JobsTrouble-shootingPlanning, Decision-MakingPoorly Mastered Response SequencesAllocate Jobs to Slave SystemsThe Central Executive• Most complex and least understood component of WM• “In some ways the central executive functions more like an attentional system than a memory store” - Baddeley (1997)• “our initial specification of the CE was so vague as to serve as little more than a ragbag…” Baddeley (1996).• Model suggests CE coordinates the activity of the two slave systems• Other potential roles for the CE include coordinating retrieval strategies, selective attention, temporary activation of long term memory, suppression of habitual responses.• Baddeley suggests that a model of action control developed by Norman and Shallice (1980,1986) may serve as a model of the central executivePerceptualSystemTriggerDataBaseSupervisory AttentionalSystemEffectorSystemContentionSchedulingSchema ControlUnitsInhibitionNorman and Shallices (1986)model of attentional control2Evidence for the CEDual task performance and DAT:Random number generation:• Ss required to generate random sequences of letters make more repetitions and stereotyped responses the faster the task• Dominant schema (ABC, ITV etc) must be constantly inhibited by the SAS and novel schema activated.• Pursuit rotor and digit span tasks were adjusted so that individual performance was identical in DAT and matched controls• Combining the two tasks caused greater costs in the DAT patients than the controls - CE impaired in DATNeuropsychological evidence: - Dysexcutive SyndromeOriginal Norman and Shallice model developed to account for behaviour of patients with frontal lobe lesions.Utilisation behaviour - Lhermite (1983)Perseveration - patients have lost ability to interrupt ongoing schemasDistractibility - schemas easily “captured” by external/internal stimuliCatatonia - patients can remain motionless and speechless for hours - unable to initate schemas.Evidence for the CEUtilisation BehaviourUtilisation behaviour:The tendency to grasp common objects when presented, and perform the function commonly associated with the objectE.g Lhermite (1983)Phonological Loop Maintaining WM Activation Requires Rehearsal Silent Speech Recruits the Phonological Loop Capacity LimitationsDifficulty Rehearsing Multiple Items to Keep them ActiveSpinning Plates AnalogyWord Length EffectChadBurmaGreeceCubaMalta4.17/5CzecholslovakiaSomalilandNicaraguaAfghanistanYugoslavia2.8/5Speech Rate & Serial Recall3Word Length Effect Depends on Articulatory LoopWord Length Effects0%20%40%60%80%100%AuditoryPresentationw/SuppressionVisualPresentationw/SuppressionAuditoryPresentationw/oSuppressionVisualPresentationw/oSuppressionCorrectly RecalledShortLongPhonological Loop: Take 2 Passive Phonological StoreSpeech PerceptionArticulatory ProcessesLinked to Speech ProductionGives Access to Phonological StorePhonological Loop: Take 2PhonologicalStoreArticulatoryControl ProcessesVisual WordPresentationAuditoryWordPresentationVisuospatial Sketchpad Geographical Orientation Planning Spatial Tasks Visual ImaginationEngineeringArchitecture“a system especially well adapted to the storageof spatial information, much as a pad of paper might be used to work out a geometric puzzle.”-- BaddelyBrooksVerbal ResponsePointing ResponseTapping ResponseThe cow jumped over the moon.(no, yes, no, no, no, yes)Brooks’ Data4Visuospatial Sketchpad Loop vs. SketchpadEpisodic BufferRecent addition to modelExplains how people can recall things when doing articulatory suppressionBackup storeSupports serial recallIntegrates information from visual and auditory modalitiesBaddely’s Revised WM ModelCentral ExecutiveVisuospatial Sketch PadPhonological StoreEpisodic BufferVisual SemanticsEpisodicLTMLanguageNN Approach to MemoryLTM – connection strengths among nodesWM – activation “Transfer” to LTM is learningCapacity Limitations – limitations on total level of activationWM in NNs Rehearsal Resonant positive feedback loops Interference EffectsLateral inhibition btw. nodes coding similar items Set Size EffectsActivation limitations Serial Order EffectsLateral inhibition most affects items in the middle1 2 3L1L2Lateral InhibitionRehearsal is ResonanceStimulus 1 Stimulus 2 Stimulus 35Fun Facts about WMItems in WM defined by a high level of activationIf unattended, items in WM decay Items maintained in WM via rehearsal to keep them in activated state(more) Fun Facts about WMNumber of items one can maintain in WM is limitedLimitations of WM depend on rehearsal capacityAs items in WM decay, activation level and access speed go downWorking Memory Executive Processor Visuospatial Sketchpad Phonological Loop Continually interacting w/perceptual, motor, and different components of LTM